| Step | Hyp | Ref | Expression | 
						
							| 1 |  | btwnexchand.1 |  |-  ( ph -> N e. NN ) | 
						
							| 2 |  | btwnexchand.2 |  |-  ( ph -> A e. ( EE ` N ) ) | 
						
							| 3 |  | btwnexchand.3 |  |-  ( ph -> B e. ( EE ` N ) ) | 
						
							| 4 |  | btwnexchand.4 |  |-  ( ph -> C e. ( EE ` N ) ) | 
						
							| 5 |  | btwnexchand.5 |  |-  ( ph -> D e. ( EE ` N ) ) | 
						
							| 6 |  | btwnexchand.6 |  |-  ( ( ph /\ ps ) -> B Btwn <. A , C >. ) | 
						
							| 7 |  | btwnexchand.7 |  |-  ( ( ph /\ ps ) -> C Btwn <. A , D >. ) | 
						
							| 8 |  | btwnexch |  |-  ( ( N e. NN /\ ( A e. ( EE ` N ) /\ B e. ( EE ` N ) ) /\ ( C e. ( EE ` N ) /\ D e. ( EE ` N ) ) ) -> ( ( B Btwn <. A , C >. /\ C Btwn <. A , D >. ) -> B Btwn <. A , D >. ) ) | 
						
							| 9 | 1 2 3 4 5 8 | syl122anc |  |-  ( ph -> ( ( B Btwn <. A , C >. /\ C Btwn <. A , D >. ) -> B Btwn <. A , D >. ) ) | 
						
							| 10 | 9 | adantr |  |-  ( ( ph /\ ps ) -> ( ( B Btwn <. A , C >. /\ C Btwn <. A , D >. ) -> B Btwn <. A , D >. ) ) | 
						
							| 11 | 6 7 10 | mp2and |  |-  ( ( ph /\ ps ) -> B Btwn <. A , D >. ) |